Two giant planets lighter than cotton candy are giving astronomers a rare new window into the origins of some of the galaxy’s strangest worlds. The unusual worlds belong to a rare class known as “super-puff” planets, and both are less dense than cotton candy. Cotton candy typically has a density of about 0.05 grams per cubic centimeter, meaning both planets are even less dense. How Do Super-Puff Planets Form? Scientists have not yet reached a consensus on how super-puff planets become so large while remaining so light.